The invention relates generally to marine propulsion systems and, more particularly, to outboard motors including propulsion units which are steerable in a generally horizontal plane and tiltable in a generally vertical plane.
The invention also relates to tilt/trim subsystems for power tilting/trimming of propulsion units between a lower normal running position in which the propeller is submerged in water, and a tilted or raised position in which the propeller is located for above-the-water accessibility.
Relatively small vessels, such as motor boats or the like, generally use a tilt-trim subsystem. Known tilt-trim subsystems typically comprise a tilt cylinder unit for swinging a swivel bracket through a relatively large angle to lift the lower portion of the outboard motor above the water level or, conversely, lower the outboard motor below the water level. Such subsystems may further comprise a distinct trim cylinder unit for angularly moving the swivel bracket through a relatively small angle to trim the outboard motor while the lower portion thereof is being submerged. One desirable characteristic of a tilt-trim subsystem would be to provide a slower rate of rotation during trimming to retain the propulsion unit in water for a longer interval during movement thereof through a predetermined angular trim range and thereafter to more rapidly elevate the propulsion unit from the water so as to reach a full tilt-up position. Unfortunately, previous tilt-trim subsystems, as suggested above, may require use of distinct tilt and trim cylinder units or have required use of fairly complex mechanical structures to somewhat meet the tilt-trim requirements of the propulsion unit. Thus, it would be desirable to provide a single cylinder/piston subassembly that would allow to meet the trim-tilt requirements of the propulsion unit. It would be further desirable for that subassembly to provide a relatively slower rate of rotation during trimming, as compared to the rate of rotation used to reach a fully tilt-up position. The tilt-trim subsystem should allow for a low-cost and uncomplicated mechanical installation capable of being installed in kit form and capable of being serviced without requiring substantial time and expenditures.